how to slice onions

This is the fastest, easiest, and safest technique I have seen to slice onions.

If you need onion rings, the only safe way to do this is with a mandolin. This guide is for evenly sliced half onion pieces.

Onions have a natural set of layers that this technique takes advantage of. You will end up with similarly sized pieces of onion that will cook consistently.

You must use a sharp knife. A sharp knife is safer, as it is much less likely to slip than a blunt one. Also, it is less likely to bruise the onion, which will reduce the release of the aromatics which make your eyes water.

You will notice that the technique keeps the cut sides of the onion down, which again reduces the exposure to these aromatics. This will stabilise the onion whilst you prepare it, reducing the risk of cutting yourself.

You should make sure you have a damp cloth under the chopping board to stop it from slipping.

the method

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  • damp cloth
  • chopping board
  • chef's knife


  • 1 onion


  • Place the chopping board on a damp cloth. Remove any loose papery skin from the onion to stop your knife from slipping when making the first cut.
    An onion on a chopping board
  • Cut off the root end of the onion.
    An onion on a chopping board showing the root end removed
  • Stand the onion on the cut root end and slice the onion in half downwards from stalk to root end.
    An onion on a chopping board showing the cut to halve the onion.
  • Take one onion half and carefully peel away the papery outside layers.
    An onion half on a chopping board after peeling paper skin
  • Now cut off the stalk end.
    An onion on a chopping board showing the root and stem ends removed
  • Turn the onion so one of the cut ends is facing you. Hold the onion with your fingers curled under and use your second finger knuckle to guide the blade. Slice from one cut end to the other, at the required thickness.
    An onion on a chopping board showing cut across along onion


  • Always put a damp cloth under the chopping board to prevent it from slipping.

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